1. Field
One or more exemplary embodiments relate to a laser optical system and a laser annealing device including the same.
2. Description of the Related Art
A laser is used in many industries for a variety of purposes. For example, poly-crystalline silicon, which is used in a thin film transistor of an organic light-emitting display device or a liquid crystal display device, is prepared by crystallizing amorphous silicon according to an annealing method using a laser.
Such an annealing method using a laser to form a poly-crystalline silicon layer as an active layer on a substrate is performed by irradiating an entire surface of the substrate with a linear beam having a constant length and a constant width. Here, the irradiation is performed by scanning the substrate with the linear beam.
A pulse laser beam of an excimer laser is mainly used as the laser beam for the annealing method. A cross-sectional shape of a laser beam (that irradiates the substrate for a set or predetermined period of time) influences a crystalline structure of the poly-crystalline silicon, and furthermore, will have a variety of impacts on quality of a display device.
Therefore, it has become an important issue to control not only the amount of time that the substrate is irradiated with the laser beam, but also the cross-sectional shape of the laser beam.